This CRL Screen Frame Notching Jig and Tool Assembly notches roll-form screen frame for the installation of tension springs, slide locks, and knife latches. The grooved wooden jig holds 1/4, 5/16, 3/8, 7/16 and 1/2 inch (6.4, 7.9, 9.5, 11.1 and 12.7 millimeter) screen frame securely while you notch the metal with the notching tool, which is included. It is extremely simple, easy to use and a real time saver.